diff --git a/src/openvpn/integer.h b/src/openvpn/integer.h
index 9bb00a38..51085450 100644
--- a/src/openvpn/integer.h
+++ b/src/openvpn/integer.h
@@ -77,6 +77,20 @@ constrain_int(int x, int min, int max)
     }
 }
 
+/** Return true if the addition of a and b would overflow. */
+static inline bool
+time_t_add_overflow(time_t a, time_t b) {
+    static_assert(((time_t) -1) < 0, "OpenVPN assumes time_t is signed");
+    static_assert(((time_t) .9) == 0, "OpenVPN assumes time_t is integer type");
+    static_assert(sizeof(time_t) == sizeof(long) || sizeof(time_t) == sizeof(long long),
+        "OpenVPN assumes that time_t is of type long int or long long int");
+    static const time_t TIME_MAX = sizeof(time_t) == sizeof(long) ?
+            LONG_MAX : LLONG_MAX;
+    static const time_t TIME_MIN = sizeof(time_t) == sizeof(long) ?
+            LONG_MIN : LLONG_MIN;
+    return (a > 0 && b > TIME_MAX - a) || (a < 0 && b < TIME_MIN - a);
+}
+
 /*
  * Functions used for circular buffer index arithmetic.
  */
diff --git a/src/openvpn/interval.c b/src/openvpn/interval.c
index 16343865..909e3fcd 100644
--- a/src/openvpn/interval.c
+++ b/src/openvpn/interval.c
@@ -51,11 +51,13 @@ event_timeout_trigger(struct event_timeout *et,
 
     if (et->defined)
     {
-        int wakeup = (int) et->last + et->n - local_now;
+        ASSERT(!time_t_add_overflow(et->last, et->n));
+        time_t wakeup = et->last + et->n - local_now;
         if (wakeup <= 0)
         {
 #if INTERVAL_DEBUG
-            dmsg(D_INTERVAL, "EVENT event_timeout_trigger (%d) etcr=%d", et->n, et_const_retry);
+            dmsg(D_INTERVAL, "EVENT event_timeout_trigger (%d) etcr=%d", et->n,
+                 et_const_retry);
 #endif
             if (et_const_retry < 0)
             {
@@ -72,7 +74,8 @@ event_timeout_trigger(struct event_timeout *et,
         if (tv && wakeup < tv->tv_sec)
         {
 #if INTERVAL_DEBUG
-            dmsg(D_INTERVAL, "EVENT event_timeout_wakeup (%d/%d) etcr=%d", wakeup, et->n, et_const_retry);
+            dmsg(D_INTERVAL, "EVENT event_timeout_wakeup (%ld/%d) etcr=%d",
+                 (long) wakeup, et->n, et_const_retry);
 #endif
             tv->tv_sec = wakeup;
             tv->tv_usec = 0;